RU2562970C2 - Separator having heat-resistant insulating layers - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention claims a separator (1) having heat-resistant insulating layers for an electric device, which includes a polymer-based porous substrate (2) and heat-resistant insulating layers (3) formed at both surfaces of the polymer-based porous substrate (2) and heat-resistant particles having the melting point or the point of thermal softening of 150°C or more. The claimed separator is characterised by an optimal parameter in compliance with which the total thickness of the heat-resistant insulating layer is selected so that it ensures the optimal resistance of liquid electrolyte.

EFFECT: claimed separator also has sufficient mechanical strength and prevents short circuiting.

8 cl, 7 dwg, 1 tbl, 12 ex

Description

FIELD OF TECHNOLOGY

The present invention relates to a separator having heat-resistant insulating layers.

BACKGROUND

There is a great need to reduce carbon dioxide in order to cope with the problems of air pollution and global warming. In the automotive industry, strong expectations for carbon emissions reduction are associated with the proliferation of electric vehicles (EV) and hybrid electric vehicles (HEV). Thus, the development of electrical devices, such as batteries for drive electric motors, is actively being carried out as a key factor for the practical use of such vehicles.

In particular, lithium-ion batteries are preferably used for electric vehicles due to the high energy density and durability with respect to recharge and discharge, and therefore, batteries tend to have large capacities. As a result, lithium-ion batteries must additionally provide reliability.

Rechargeable lithium-ion batteries generally include positive electrodes containing the active material of the positive electrode deposited on both surfaces of the collector of the positive electrode, and negative electrodes containing the active material of the negative electrode deposited on both surfaces of the collector of the negative electrode. Each positive electrode and each negative electrode are connected to each other through an electrolyte layer, which includes a separator holding the electrolyte solution or electrolyte gel. Several sets of positive electrode, negative electrode and separator are placed in the battery case.

For example, a polyolefin microporous film having a thickness in the range of about 20-30 microns is widely used as a separator. However, such a polyolefin microporous film has a risk of thermal contraction due to an increase in temperature in the battery and a short circuit in association with thermal contraction.

In order to suppress thermal compression, improvements are being made during the development of separators having heat-resistant insulating layers in which heat-resistant porous layers are laid on the surfaces of a microporous film. For example, Patent Document 1 studies that such a separator is used for a winding lithium-ion battery in order to suppress thermal compression caused by an increase in temperature in the battery.

PATENT DOCUMENTS

Patent Document 1: Publication WO 2007/066768.

SUMMARY OF THE INVENTION

However, if the separator described in Patent Document 1 is used for a flat multilayer battery with a non-aqueous electrolyte, the edge portion of the separator may be bent during manufacture of the battery, and the separator with the bent edge portion is laid and laminated. In particular, in the case of a large battery used for an electric vehicle, since each cell has a large area, even a slight curvature can lead to a battery defect during operation, which leads to a large decrease in yield.

The present invention has been made in view of a traditional problem. An object of the present invention is to provide a separator having heat-resistant insulating layers capable of preventing bending so as to stably produce an electrical device with high reliability.

A separator having heat-resistant insulation layers according to an aspect of the present invention includes a polymer-based porous substrate and heat-resistant insulation layers formed on both surfaces of the polymer-based porous substrate and containing heat-resistant particles having a melting point or a thermal softening point of 150 ° C or above. The parameter X represented by the following mathematical formula 1 is greater than or equal to 0.15.

Mathematical formula 1

In the formulas, A ′ and A ”represent the thicknesses (μm) of the respective heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate under the condition A'≥A”, and C represents the total thickness (μm) of the separator having heat-resistant insulation layers.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a cross-sectional view showing an exemplary planar multilayer non-bipolar lithium ion secondary battery according to an embodiment of the present invention.

2 is a schematic view showing a separator having heat-resistant insulating layers according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a separator having heat-resistant insulating layers according to an embodiment of the present invention.

FIG. 4 is a perspective view showing a typical appearance of a flat multilayer non-bipolar lithium ion secondary battery according to an embodiment of the present invention.

5 is a schematic view for explaining a method for measuring the height of the bend in the examples.

6 is a graph showing the relationship between parameter X and the bend height of the separator prepared in each of the examples and comparative examples.

7 is a graph showing the relationship between the parameter Y, the height of the bend and the yield characteristic of the separator prepared in each of the examples and comparative examples.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A separator having heat-resistant insulating layers for an electric device according to the present invention and an electric device using such a separator are explained in more detail below with reference to the drawings. It should be noted that identical elements in the following explanation of the drawings are indicated by identical reference numbers, and their overlapping explanations are not repeated. In addition, the aspect ratios in the drawings are increased for convenience of explanation and may differ from actual ratios.

A separator having heat-resistant insulating layers for an electric device according to an embodiment of the present invention, and an electric device using such a separator, are not susceptible to an unimpeded defect during laying of each element, even when the electric device is a large flat layered electric device. This improves productivity. Therefore, an electrical device using a separator having heat-resistant insulating layers according to the present embodiment, in particular a non-aqueous electrolyte battery, is preferably used as a power source for driving or an auxiliary vehicle power source.

The electrical device according to the present embodiment is not particularly limited with respect to the constituent elements, provided that a separator is used having heat-resistant insulating layers as explained below. In the present embodiment, a lithium ion battery is illustrated as an example of an electrical device.

As an example of using a lithium-ion battery, a lithium-ion primary cell battery or a lithium-ion secondary battery are possible. Since the separator has a high cyclic durability, it is preferably used as a lithium-ion battery for use in a power source for driving a vehicle or in a mobile device such as a mobile phone.

A separator having heat-resistant insulating layers can be used for a flat multilayer (flat shape) battery. The design of a flat multilayer battery contributes to long-term reliability due to simple sealing technology, such as thermal adhesion, and has an advantage in cost and operational efficiency.

From the point of view of the electrical connection (electrode design) in the lithium-ion battery, the present embodiment is applicable not only to a non-bipolar battery (with internal parallel connection), but also to a bipolar battery (with internal serial connection).

A separator having heat-resistant insulating layers can be used for a battery with an electrolyte in the form of a solution using an electrolyte in the form of a solution, such as a non-aqueous electrolyte solution. The separator can also be used for an electrolyte layer used, for example, in a gel electrolyte battery using a polymer gel electrolyte.

Hereinafter, a non-bipolar lithium ion secondary battery using a separator having heat-resistant insulating layers according to the present embodiment is explained with reference to the drawings.

General battery design

Figure 1 shows the overall construction of a flat multilayer (flat shape) lithium ion secondary battery according to an embodiment of the present invention. Hereinafter, a flat multilayer lithium ion secondary battery may be referred to simply as a “multilayer battery".

As shown in FIG. 1, the multilayer battery 10 according to the present embodiment has a configuration in which a substantially rectangular electric power generating element 21, in which a charge-discharge reaction actually takes place, is sealed in the outer battery element 29. The electric power generating element 21 has a configuration in which positive electrodes, electrolyte layers and negative electrodes are stacked on top of each other. Each positive electrode has a configuration in which layers 13 of the active material of the positive electrode are provided on both surfaces of the collector 11 of the positive electrode. Each electrolyte layer 17 has a configuration in which an electrolyte (electrolyte solution or electrolyte gel) is held in a separator. Each negative electrode has a configuration in which layers 15 of the active material of the negative electrode are provided on both surfaces of the collector 12 of the negative electrode. In other words, several sets of a positive electrode, an electrolyte layer and a negative electrode arranged in this order are stacked on top of each other so that one layer 13 of the active material of the positive electrode faces one layer 15 of the active material of the negative electrode with the electrolyte layer 17 between them.

The positive electrode, the electrolyte layer and the negative electrode, which are adjacent to each other, by virtue of this, constitute a layer of 19 single cell cells. Namely, the multilayer battery 10 shown in FIG. 1 has a structure in which several layers 19 of single cell cells are stacked on top of each other so that they are electrically connected in parallel. Here, the positive electrode down conductors located in the outermost layers of the electric power generating element 21 comprise a positive electrode active material layer 13 on only one side. Alternatively, the positive electrode down conductors may comprise layers 13 of active material of the positive electrode on both sides. Namely, a collector containing layers of active material of the positive electrode on both sides can be used as a collector in the outermost layer, in addition to the case where the collector in the outermost layer is a collector in which the layer of active material is provided on only one side . Similarly, negative electrode down conductors, each of which contains a negative electrode active material layer on one side or on both sides, can be located in the outermost layers of the electric power generating element 21 such that the positions of the positive electrode and negative electrode shown in FIG. 1, swap places.

The positive electrode collector plate 25 and the negative electrode collector plate 27, which are electrically conductive to the respective electrodes (positive electrode and negative electrode), are connected to the positive electrode collector 11 and the negative electrode collector 12, respectively. The positive electrode collector plate 25 and the negative electrode collector plate 27 are held by each end portion of the external battery element 29 and are open outside the external battery element 29. The positive electrode collector plate 25 and the negative electrode collector plate 27 can be connected to the positive electrode collector 11 and the negative electrode collector 12 of the respective electrodes through the output of the positive electrode and the output of the negative electrode (not shown), for example, by ultrasonic welding or resistance welding.

The lithium-ion battery described above is distinguished by a separator. Further in this document, the main constituent elements of a battery including a separator are described.

Active material layer

The positive electrode active material layer 13 and the negative electrode active material layer 15 contain the active material and other additives as necessary.

The positive electrode active material layer 13 contains the positive electrode active material. Examples of the active material of the positive electrode include a complex oxide of lithium and a transition metal, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni-Co-Mn) O ₂ and an oxide in which a portion of each of these transition metals replaced by other elements; phosphate compound of lithium and transition metal; and a sulfate compound of lithium and a transition metal. Two or more kinds of these positive electrode active materials may be used together as appropriate. Given the characteristics of capacitance and power, complex lithium oxide and transition metal oxide are preferably used as the active material of the positive electrode. Active positive electrode materials other than those described above may also be used.

The negative electrode active material layer 15 contains the negative electrode active material. Examples of the active material of the negative electrode include carbon material, for example, graphite, soft carbon and hard carbon; composite oxide of lithium and a transition metal (for example, Li ₄ Ti ₅ O ₁₂ ); metal material; and a negative electrode material based on a number of lithium alloys. Two or more kinds of these negative electrode active materials may be used together as appropriate. Given the characteristics of capacity and power, a carbon material or a complex oxide of lithium and a transition metal is preferably used as the active material of the negative electrode. Active negative electrode materials other than those described above may also be used.

The average particle diameter of the respective active materials contained in the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited; however, it is preferably in the range of 1-100 μm, more preferably 1-20 μm, taking into account the higher power characteristics.

The positive electrode active material layer 13 and the negative electrode active material layer 15 preferably comprise a binder. The binder used in the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited. Examples of a binder include a thermoplastic polymer such as polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene butucene butadiene (SB) , butadiene rubber, ethylene propylene rubber, copolymer of ethylene and propylene diene, a block copolymer of styrene, butadiene and styrene and its hydrogen additive, as well as a block copolymer of styrene, isoprene and styrene and its waters natural supplement. The binder may also be a fluoride polymer such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), a copolymer of tetrafluoroethylene and perfluoroalkylvinyl ether (PFA), an ethylene copolymer (PCTFE), tetrafluoroethylene tetrafluoroethylene). , a copolymer of ethylene and chlorotrifluoroethylene (ECTFE) and polyvinyl fluoride (PVF). Other examples of a binder include vinylidene fluoride-based fluorine rubber, for example, vinylidene fluoride and hexafluoropropylene fluoride rubber (VDF-HFP fluoride rubber), vinylidene fluoride, hexafluoropropylene and fluorine rubber fluoride rubber (F fluoride rubber F, D-based fluorine rubber), based on vinylidene fluoride and pentafluoropropylene (fluororubber based on VDF-PFP), fluorinated rubber based on pentafluoropropylene and tetrafluoroethylene (fluorinated rubber based on VDF-PFP-TFE), fluorinated rubber based on vinylidene fluoride, perfluoromethylvinyl ether pa and tetrafluoroethylene (fluoroelastomer based on VDF-PFMVE-TFE) and vinylidene fluoride fluororubber based on chlorotrifluoroethylene (fluoroelastomer based on VDF-CTFE). Another other example of a binder is an epoxy polymer. Of these, polyvinylidene fluoride, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile and polyamide are particularly preferred. These binders are suitable for use in active material layers because these binders have high heat resistance, have a sufficiently wide potential window and are stable both with respect to the potential of the positive electrode and with respect to the potential of the negative electrode. Binders can be used individually or in combination of two or more.

The amount of binder contained in the respective layers of the active material is not specifically limited as long as the amount is sufficient to bind the active material. However, the amount of binder is preferably in the range of 0.5-15% by weight, more preferably in the range of 1-10% by weight, relative to each layer of active material.

Examples of other additives contained in the respective layers of the active material include an electrically conductive additive, an electrolyte salt (lithium salt), and an ion-conductive polymer.

An electrically conductive additive is an additive added to increase the electrical conductivity in the positive electrode active material layer or the negative electrode active material layer. The electrically conductive additive may be a carbon material, such as carbon black (for example, acetylene black), graphite, and carbon fiber. Adding an electrically conductive additive to the active material layers contributes to the efficient establishment of an electronic network in the active material layers and to improving battery power characteristics.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiC1O ₄ , LiAsF ₆ and LiCF ₃ SO ₃ .

Examples of the ion-conducting polymer include a polyethylene oxide (PEO) polymer and a polypropylene oxide (PPO) polymer.

The mixing ratio of the components contained in each layer of the active material of the positive electrode and the layer of active material of the negative electrode is not particularly limited. The mixing ratio can be adjusted by appropriate reference to the known data obtained on non-aqueous batteries. The thickness of the respective active material layers is not specifically limited, and it is possible to appropriately refer to known battery data. As an example, the thickness of the respective layers of active material may be in the range of about 2-100 microns.

Down conductor

The collector 11 of the positive electrode and the collector 12 of the negative electrode are made of electrically conductive material. The size of the down conductors can be determined depending on the intended use of the battery. For example, down conductors having large areas are used for a large battery that requires a high energy density. The lithium ion battery according to the present embodiment is preferably a large battery, and the collectors used therein, for example, have a long side of 100 mm or more, preferably have a size of 100 mm × 100 mm, more preferably 200 mm × 200 mm. The thickness of down conductors is not specifically limited; however, the thickness is approximately in the range of 1-100 μm. The shape of down conductors is not limited in a specific way. The multilayer battery 10 shown in FIG. 1 may use a down conductor foil or a contour down conductor (example, expanded grids).

The material contained in the respective down conductors is not particularly limited; however, metal is preferably used. Examples of the metal include aluminum, nickel, iron, stainless steel, titanium and copper. In addition, a clad metal of nickel and aluminum, a clad metal of copper and aluminum, or an alloyed material of these metals combined with each other is preferably used. A foil may also be used in which the metal surface is coated with aluminum. In particular, aluminum, stainless steel and copper are preferred given the battery potential and electronic conductivity.

Electrolyte layer

The electrolyte layer 17 has a structure in which the electrolyte is held in a central portion in the direction of the plane of the separator according to the present embodiment. The use of the separator according to the present embodiment allows to prevent bending of the edge sections of the separator during installation, thereby stably making the battery with high reliability.

Separator having heat resistant insulation layers

A separator having heat-resistant insulation layers according to the present embodiment includes a polymer-based porous substrate and heat-resistant insulation layers formed on both surfaces of the polymer-based porous substrate and including heat-resistant particles having a melting point or thermal softening point of 150 ° C or higher. The separator is characterized in that the parameter X represented by the following mathematical formula (1) is greater than or equal to 0.15.

Mathematical formula 1

In the formulas, A ′ and A ”represent the thicknesses (μm) of the heat-resistant insulation layers formed on both surfaces of the porous polymer-based substrate when the condition A'≥A” is satisfied, and C represents the total thickness (μm) of a separator having heat-resistant insulation layers.

The separator according to the present embodiment allows to prevent bending or bending of the edge portions. Therefore, the separator according to the present embodiment contributes to increasing the yield of products in the manufacturing process of flat multilayer batteries. If parameter X is below 0.15, the probability of bending cannot be ignored. As a result, the yield of products is significantly reduced, in particular when large-sized flat multilayer batteries are manufactured.

In the separator described in Patent Document 1, a defect during laying due to bending of the separator does not occur unhindered when the separator is used for a winding battery. However, when the separator is used for a large flat layered battery, such as a lithium-ion battery for an electric vehicle, even a slight distortion can lead to a defect during the laying operation, since each cell has a large area. For example, as shown in FIG. 2 (a), when a large flat layered battery is manufactured, the negative electrode 5, the separator 1, and the positive electrode 4 are generally sequentially transferred using the stacking arm and stacked at high speed. However, since the separator is made of relatively soft material, if a part of the separator is bent during transfer, as shown in FIG. 2 (b), the separator having the raised part is layered in a multilayer object. The raised part is then pressed, and the separator due to this is stacked, while the bent and raised part are bent in a multilayer object. This leads to a short circuit, which significantly reduces the yield of suitable products and therefore increases costs.

With this in mind, as shown in FIG. 3, the separator 1 having heat-resistant insulation layers according to the present embodiment has a structure in which heat-resistant insulation layers 3 are provided on both surfaces of the porous polymer substrate 2.

Here, the reason the separator forms a bent portion may be because thermal stress remains when heat-resistant insulating layers are applied to the porous polymer-based substrate, and they are dried by heat, such as warm air. In particular, the porous polymer-based substrate is stretched by thermal drying, since the polymer contained in the porous polymer-based substrate has a large coefficient of linear expansion during heating. On the other hand, since heat-resistant insulating layers are made of heat-resistant particles having a melting point or thermal softening point of 150 ° C or higher, heat-resistant insulating layers have a fairly small coefficient of linear expansion in the temperature range of thermal drying and, therefore, expand very slightly. Therefore, when thermal drying after applying heat-resistant insulating layers to a porous polymer-based substrate ends and they cool to room temperature, the porous polymer-based substrate is significantly compressed, but the heat-resistant insulation layers are very slightly compressed. As a result, since there is a difference in the compression rate between the polymer-based porous substrate and the heat-resistant insulation layers, the polymer-based porous substrate tries to compress, but the heat-resistant insulation layers resist compression. Accordingly, the bend is formed in such a way that the porous polymer-based substrate bends inward.

Thus, according to the present embodiment, the heat-resistant insulating layers 3 are applied to both surfaces of the porous polymer-based substrate 2 in such a way that the thicknesses A ′, A ”of the heat-resistant insulating layers 3 are aligned as much as possible. This improves the balance of mechanical stress during compression of the heat-resistant insulating layers 3 in the vertical direction of the porous polymer-based substrate and thereby prevents bending. In addition, the thicknesses A ′, A ″ of the heat-resistant insulating layers are adjusted so that they have a specific relationship with the total thickness C of the separator. Accordingly, the balance between the internal mechanical stress of the porous polymer-based substrate 2 and the mechanical stress when compressing the heat-resistant insulating layers 3 is improved so as to sufficiently prevent bending. Additionally, the parameter X represented by the mathematical formula (1) is set to be greater than or equal to 0.15. This prevents the occurrence of a large bend, so that the problem of bending and layering of the bend during the laying operation is solved.

Parameter X, represented by mathematical formula (1), is an index indicating the difference in mechanical stress during compression of heat-resistant insulating layers formed on both surfaces of a porous polymer-based substrate caused by drying. As the value of X becomes smaller, the difference in mechanical stress during compression of the heat-resistant insulating layers is more evident. When the difference in compressive stress in the heat-resistant insulation layers on both surfaces of the polymer-based porous substrate is large relative to the internal mechanical stress of the polymer-based porous substrate, a bend is often formed. For example, as the thicknesses A ′, A ″ of the heat-resistant insulation layers decrease with respect to the total thickness C of the separator, the parameter X decreases. In addition, the value X decreases when the difference in thickness of the heat-resistant insulation layers on both surfaces of the porous polymer substrate is large due, for example, to significant differences in the weight of heat-resistant insulating layers on both surfaces of a porous polymer-based substrate. The parameter X is set to be greater than or equal to 0.15, preferably greater than or equal to 0.20. If the X value is lower than 0.15, the probability of bending cannot be ignored, and as a result, the yield of products is significantly reduced when large-sized flat multilayer batteries are manufactured. It should be noted that the "weight" in this case represents the weight (g / m ² ) of heat-resistant insulating layers per unit area of the porous polymer-based substrate.

The upper limit of the parameter X represented by the mathematical formula (1) is not particularly limited, provided that the bending of the separator is prevented. For example, the upper limit may be 0.1.

In the separator according to the present embodiment, the parameter Y represented by the following mathematical formula (2) is preferably in the range of 0.3-0.7.

Mathematical Formula 2:

In the formula, X represents the same value as described above, and D represents the porosity of the respective heat-resistant insulating layers 3.

As described above, in the separator according to the present embodiment, as the parameter X represented by the mathematical formula (1) becomes large, the bend does not form unobstructed in the edge portion of the separator. However, when the thicknesses (A ′, A ″) of the heat-resistant insulating layers increase, the value of X increases, but the ion permeability decreases, and the yield characteristics of the products deteriorate. The inventors analyzed conditions to maintain the high yield characteristics of the products while preventing bending, and as a result, the inventors found that the porosity (D in the mathematical formula (2)) of the heat-resistant insulating layers is a factor in determining the yield characteristics of the products. Namely, in order to prevent bending, as well as to provide a high yield characteristic, it is important that two heat-resistant insulating layers uniformly press both surfaces of the porous polymer-based substrate with proper pressure. If the pressure is too small or unbalanced, a bend is often formed. If the pressure is too strong, the ion permeability decreases, which can lead to a deterioration in the yield characteristics of the battery.

The parameter Y, represented by mathematical formula (2), is an index indicating the strength and uniformity with which two heat-resistant insulating layers press on both surfaces of the porous polymer-based substrate. For example, the Y value decreases when the pressure applied to both surfaces of the porous polymer-based substrate is unbalanced due to, for example, significant differences in the weight of the heat-resistant insulation layers on both surfaces of the porous polymer-based substrate. In addition, the Y value also decreases when the pressure from the heat-resistant insulation layers is small, because the heat-resistant insulation layers are thin, or the porosity is large. Additionally, the Y value decreases as the overall thickness C of the separator increases. On the other hand, the Y value increases when the pressure from the heat-resistant insulation layers is large, because the heat-resistant insulation layers are thick, or the porosity is large. In the separator according to the present embodiment, the parameter Y is preferably in the range of 0.3-0.7, more preferably in the range of 0.35-0.65. When the Y value is greater than or equal to 0.3, the bend does not form unhindered. If the Y value is less than or equal to 0.7, a high yield characteristic can be provided.

In mathematical formulas (1) and (2), the values measured with a micrometer can be used as the thicknesses A ', A ”of the heat-resistant insulating layers and the total thickness C of the separator. The porosity D (%) of the heat-resistant insulating layers can be obtained by the following mathematical formula (3) using the mass Wi (g / cm ² ) per unit area of each component “i” contained in the heat-resistant insulating layers, density di (g / cm ³ ) of each component “i” and thickness “t” (cm) of the corresponding heat-resistant insulating layers. It should be noted that when heat-resistant insulating layers on both surfaces of a porous polymer-based substrate have different porosities, the average value of porosities is specified as porosity D (%).

Mathematical Formula 3:

Heat-resistant insulating layers 3 are provided on both surfaces of the polymer-based porous substrate 2 in the stacking direction, namely, in the stacking direction of the positive electrode, negative electrode and electrolyte layer 17. As shown in FIG. 3, the heat-resistant insulating layers 3 are preferably laid directly on both surfaces of the porous polymer substrate 2 in such a way that they are located opposite each other. Additionally, heat-resistant insulating layers 3 are preferably formed on both surfaces of the porous polymer substrate 2. As shown in FIG. 3, each of the heat-resistant insulating layers 3 may have a single layer structure or may have a multilayer structure. When each of the heat-resistant insulating layers 3 includes several layers, the layers can be made of various materials.

Hereinafter, a separator according to the present embodiment is explained in more detail in this document.

Polymer-based porous substrate

Examples of the polymer-based porous substrate 2 include a porous sheet and a woven material or non-woven material containing an organic polymer that absorbs and retains the electrolyte. Preferred examples of the organic polymer contained in the porous polymer-based support include a polyolefin, for example, polyethylene (PE) and polypropylene (PP); polyimide or aramid; and polyester, for example polyethylene terephthalate (PET). The average value of the diameters of small pores (average diameter of small pores) formed in a porous polymer-based substrate is preferably in the range of 10 nm to 1 μm. The diameters of small pores can be obtained, for example, by means of a nitrogen gas adsorption method. The thickness of the porous polymer-based support is preferably in the range of 1-200 μm. The porosity of the porous polymer-based support is preferably in the range of 20-90%.

The porous polymer-based substrate is explained in more detail below. The porous sheet used as the polymer-based porous substrate is a microporous film containing a finely porous polymer. Examples of such a polymer include a polyolefin, for example, polyethylene (PE) and polypropylene (PP); a multilayer object having a three-layer structure of PP / PE / PP; and polyimide or aramid. In particular, a microporous polyolefin-based film is preferably used since it is chemically stable with respect to the organic solvent so as to reduce the reactivity with the electrolyte solution to a lower level.

The thickness of the porous sheet cannot be set whatever, because it depends on the intended use. However, the thickness in a single-layer or multi-layer structure is preferably in the range of 4-60 μm when used in a battery to drive a vehicle electric motor. The diameters of the micropores in the porous sheet are generally about 10 nm and preferably less than or equal to 1 μm. The porosity of the porous sheet is preferably in the range of 20-80%.

Examples of a woven material or non-woven material used for a porous polymer-based substrate include a polyester, for example, polyethylene terephthalate (PET); polyolefin, for example, PE and PP; and polyimide or aramid. The bulk density of the woven material or non-woven material is not specifically limited, provided that it can provide sufficient battery performance from the electrolyte solution contained therein. The porosity of the woven material or non-woven material is preferably in the range of 50-90%. The thickness of the woven material or non-woven material is preferably in the range of 5-200 μm, in particular, preferably in the range of 5-100 μm. When the thickness is greater than or equal to 5 μm, the electrolyte retention is high. When the thickness is less than or equal to 100 μm, the resistance does not increase excessively.

A method for preparing a porous polymer based substrate is not particularly limited. When the porous polymer-based substrate is a microporous polyolefin-based film, the porous polymer-based substrate can be prepared, for example, so that the polyolefin dissolves in the solvent, the dissolved material is extruded in a plate form, the solvent is removed from it, and the material obtained in this way method, subjected to uniaxial or biaxial stretching. Examples of the solvent include paraffin, liquid paraffin, paraffin oil, tetralin, ethylene glycol, glycerin and decalin.

Heat-resistant insulating layers (heat-resistant insulating porous layers)

In the present embodiment, the heat-resistant particles included in the heat-resistant insulating layers are made of a material having high heat resistance and a melting point or thermal softening point of 150 ° C or higher, preferably 240 ° C or higher. This material, which has high heat resistance, can effectively prevent the separator from squeezing even when the temperature in the battery reaches approximately 200 ° C. Accordingly, the induction of a short circuit between the electrodes can be prevented, so that a battery is obtained that practically does not lead to a decrease in performance due to an increase in temperature. It should be noted that in the present description of the invention, the "thermal softening point" represents the temperature at which the heated substance begins to soften and deform, and is called the Vicat softening temperature. The upper limit of the melting point or the thermal softening point of heat-resistant particles is not particularly limited; however, it may be, for example, 1500 ° C or lower.

The heat-resistant particles are preferably electrically insulated, stable with respect to the solvent or electrolyte solution used in the preparation of the heat-resistant insulating layers, and are electrochemically stable so that they do not undergo unimpeded redox reactions in the operating voltage range of the battery. The heat resistant particles can be either organic particles or inorganic particles, but are preferably inorganic particles in view of the reliability aspect. The heat-resistant particles are preferably fine particles with regard to dispersion. The fine particles used have an average secondary particle diameter (median diameter, D50), for example, in the range of 100 nm to 4 μm, preferably in the range of 300-3 μm, more preferably in the range of 500 nm to 3 μm. The average diameter of the secondary particles (median diameter) can be obtained using the dynamic light scattering method. The shape of the heat resistant particles is not particularly limited and may be substantially spherical or may be in a plate, rod or needle shape.

Inorganic particles (inorganic powder) having a melting point or a thermal softening point of 150 ° C. or higher are not particularly limited. Examples of inorganic particles include inorganic oxide, for example, iron oxide (FeO), SiO ₂ , Al ₂ O ₃ , aluminosilicate, TiO ₂ , BaTiO ₂ and ZrO ₂ ; inorganic nitride, for example, aluminum nitride and silicon nitride; poorly soluble ionic crystal, for example, calcium fluoride, barium fluoride and barium sulfate; covalent crystal, for example, silicon and diamond; and clay, for example, montmorillonite. The inorganic oxide may be a substance extracted from a source of minerals, such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine and mica, or an artificial substance thereof. Inorganic particles can be particles having electrical insulation, obtained in such a way that the surface of the electrically conductive material is coated with a material having electrical insulation, for example, the inorganic oxides described above. Examples of the electrically conductive material include metal; an electrically conductive oxide, for example SnO ₂ and tin and indium oxide (ITO); and carbonaceous material, for example carbon black and graphite. Of these, inorganic oxide particles are preferred since such particles can easily be applied to the porous polymer-based substrate as a water dispersion suspension in order to prepare the separator by a simple process. In particular, alumina (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ) and aluminosilicate are preferably used as inorganic oxide.

Examples of organic particles (organic powder) having a melting point or a thermal softening point of 150 ° C. or higher include several types of crosslinked polymer particles, such as crosslinked polymethylmethacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, crosslinked styrene copolymer and divinylbenzene, polyimide, melamine polymer, phenolic polymer and condensation product of benzoguanamine formaldehyde. Other examples of organic particles include heat-resistant polymer particles, for example, polysulfone, polyacrylonitrile, polyaramide, polyacetal and thermoplastic polyimide. The organic polymer contained in these organic particles can be a mixture, a modified product, a derivative, a copolymer (random copolymer, alternating copolymer, block copolymer, grafted copolymer) or a cross-linked product (in the case of heat-resistant small polymer particles) from the above materials. Of these, polymethylmethacrylate and polyaramide particles are preferably used as organic particles, taking into account industrial scale performance and electrochemical stability. Due to such particles of the organic polymer, a separator can be manufactured containing mainly polymer, which helps to reduce the weight of the battery itself.

The heat resistant particles described above can be used individually or in combination of two or more.

The thickness of the heat-resistant insulating layers using the heat-resistant particles described above is not specifically limited and is appropriately determined according to the type and intended use of the battery. However, for example, the total thickness of the heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate is preferably in the range of 5-200 μm. In the case of a battery for driving an electric motor for use, for example, in an electric vehicle or hybrid electric vehicle, the total thickness of the heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate is in the range of 5-200 μm, preferably in the range of 5 -20 microns, more preferably in the range of 6-10 microns. When the total thickness is within these ranges, high power characteristics can be provided, while the mechanical strength in the thickness direction (in the laying direction) is increased.

The thickness ratio A ′ / A ”of the heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate can be set so that it satisfies the mathematical formula (1), but preferably less than or equal to 1.2, more preferably less than or equal to 1, one. Namely, the thickness ratio A ′ / A ″ of the heat-resistant insulating layers is preferably in the range of 1.0-1.2, more preferably in the range of 1.0-1.1. The thicknesses of the heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate are preferably identical as far as possible. Accordingly, two heat-resistant insulating layers can uniformly press both surfaces of the porous polymer-based substrate to prevent bending of the separator.

The porosity of the heat-resistant insulating layers using the heat-resistant particles described above is not specifically limited, but is preferably greater than or equal to 40%, more preferably greater than or equal to 50%, taking into account the ionic conductivity. When the porosity is greater than or equal to 40%, the retention of the electrolyte (electrolyte solution or electrolyte gel) increases, so that a battery with high power characteristics is obtained. In addition, the porosity of the heat-resistant insulating layers is preferably less than or equal to 70%, more preferably less than or equal to 60%. When the porosity of the heat-resistant insulating layers is less than or equal to 70%, sufficient mechanical strength can be provided, and the effect of preventing short circuits due to foreign bodies can be increased.

The content of heat-resistant particles in the heat-resistant insulating layers is preferably in the range of 90-100% by weight, more preferably in the range of 95-100% by weight. Accordingly, two heat-resistant insulation layers can uniformly press both surfaces of the porous polymer-based substrate.

Method for manufacturing a separator

A method for manufacturing a separator according to the present embodiment is not particularly limited. For example, a separator can be made in such a way that a suspension of the composition for heat-resistant insulating layers containing heat-resistant particles having a melting point or a thermal softening point of 150 ° C or higher is applied to both surfaces of the porous polymer-based substrate, after which drying is performed.

The composition for the heat-resistant insulating layers is obtained in such a way that the heat-resistant particles are dispersed in a solvent into which an organic binder can be added as necessary. Examples of an organic binder added in order to increase the stability of the shape of the heat-resistant insulating layers include carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl butyral and polyvinyl pyrrolidone. When the composition contains an organic binder, a useful amount of the organic binder is preferably less than or equal to 10% by weight, more preferably less than or equal to 5% by weight relative to the total weight of the heat-resistant particles and the organic binder. The solvent is not particularly limited, provided that the heat-resistant particles can uniformly disperse in it. Examples of the solvent include water; aromatic hydrocarbon, for example, toluene; furfuran, for example tetrahydrofuran; ketone, for example ethyl methyl ketone, isobutyl methyl ketone and acetone; n-methylpyrrolidone; dimethylacetamide; dimethylformamide; dimethyl sulfoxide; and ethyl acetate. Ethylene glycol, propylene glycol or monomethyl acetate can be appropriately added to these solvents to control surface tension. In particular, when inorganic oxide particles are used as heat-resistant particles, water can be used as a solvent to prepare a water-dispersion suspension, so that heat-resistant insulating layers can be easily prepared. The composition for heat-resistant insulating layers is preferably prepared so as to have a concentration of solids in the range of 30-60% by weight.

The weight of the composition for heat-resistant insulating layers applied to a porous polymer-based substrate is not specifically limited, but is preferably in the range of 5-20 g / m ² , more preferably in the range of 9-13 g / m ² . It should be noted that the "weight" in this case represents the weight (g / m ² ) of the composition for heat-resistant insulating layers per unit area of the porous polymer-based substrate. When the weight is in such a range, heat-resistant insulating layers having proper porosity and thickness can be obtained. The method for applying the composition is not particularly limited, and examples thereof include a method using a knife coating device, a method using a corrugated roller coating device, a screen printing method, a method using a Meyer rod, a method using a applying device stamping method, method using a reverse roller coating apparatus, inkjet method, spray method and method using a device for coating by roller.

A method for drying a composition for heat-resistant insulating layers after coating is not particularly limited; however, warm air drying may be used.

For example, the drying temperature is in the range of 30 ° C to 80 ° C, and the drying time is in the range of 2 seconds to 50 hours.

The total thickness of the separator obtained in this way is not particularly limited; however, a range of 5-30 μm is applicable. In order to obtain a small battery, the thickness of the separator is preferably reduced as much as possible to the extent that the electrolyte layer can function quite well. Therefore, in order to reduce thickness and enhance battery power characteristics, the total thickness of the separator according to the present embodiment is preferably in the range of 20-30 μm, more preferably in the range of 20-25 μm.

The electrolyte layer is not particularly limited provided that it uses a separator according to the present embodiment. In other words, the electrolyte layer includes a separator and an electrolyte contained in a porous polymer-based substrate and in the heat-resistant insulation layers of the separator. The electrolyte held in the electrolyte layer preferably contains lithium ions and has a high lithium-ion conductivity.

In particular, the electrolyte layer may use a separator containing an electrolyte solution having a high ionic conductivity. Alternatively, an electrolyte layer may be prepared such that a gel electrolyte and the like. applied to the separator by impregnation, coating or spraying.

(a) A separator containing an electrolyte solution

With respect to the electrolyte solution allowing penetration into the separator, the electrolyte may be at least one of LiClO ₄ , LiAsF ₆ , LiPF ₅ , LiBOB, LiCF ₃ SO ₃ and Li (CF ₃ SO ₂ ) ₂ N. The solvent for the electrolyte solution may be at least one ester selected from the group consisting of ethylene carbonate (EC), propylene carbonate, diethyl carbonate (DEC), dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane and γ-butyrolactone. Preferably, an electrolyte solution is used which is prepared so that the electrolyte dissolves in the solvent and the electrolyte concentration is set in the range of 0.5 M to 2 M. However, the present invention is not limited to this electrolyte solution.

An explanation of the separator is omitted here since the separator according to the present invention described above is used.

The electrolyte solution may be held in the separator by impregnation, coating, and the like. to full capacity or can be held in the separator outside the capacity. For example, in the case of a bipolar battery, since the leakage of the electrolyte solution from the electrolyte layer can be prevented by pouring the polymer into the sealed portion of the electrolyte, impregnation may be possible outside the separator capacity to the extent that the electrolyte layer can hold the electrolyte solution. Similarly, in the case of a non-bipolar battery, since the battery cell is sealed in the external battery cell, and thus the leakage of the electrolyte solution from the external battery cell can be prevented, impregnation may be possible outside the separator capacity to the extent that the external battery cell can hold the electrolyte solution . The separator can be impregnated with an electrolyte solution by means of a conventionally known method, for example, in such a way that the electrolyte solution is poured by the filling method under vacuum, after which complete sealing is performed.

(b) Gel electrolyte layer

The gel electrolyte layer according to the present invention is obtained in such a way that the separator holds the gel electrolyte by impregnation or coating.

The gel electrolyte has a structure in which a liquid electrolyte (electrolyte solution) is poured into a matrix polymer including an ion-conducting polymer. Examples of the ion-conducting polymer used for the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof. In such a polyalkylene oxide-based polymer, an electrolyte salt, for example a lithium salt, can be sufficiently dissolved.

The relative content of the liquid electrolyte (electrolyte solution) in the gel-like electrolyte is not particularly limited, but is preferably in the range from several% by mass to 98% by mass, taking into account ionic conductivity and the like. According to the present embodiment, the gel electrolyte exhibits better effects, in particular when it contains a large amount of electrolyte solution, namely, when the relative content is greater than or equal to 70% by weight.

A gel polymer matrix polymer can provide high mechanical strength when a cross-linked structure is formed. The crosslinked structure may be formed such that the polymerizable polymer used to form the polymer electrolyte is polymerized by using an appropriate polymerization initiator. Examples of polymerization include thermal polymerization, ultraviolet polymerization, radiation polymerization, and electron beam polymerization. Examples of the polymerizable polymer used include PEO and PPO.

The thickness of the electrolyte layer is not specifically limited, but is substantially identical or slightly greater than the thickness of the separator according to the present embodiment. An electrolyte layer thickness in the range of 5-30 μm is applicable.

According to the present invention, the conventionally known various additives may be contained in the electrolyte of the electrolyte layer to the extent that the effects of the present invention are not impaired.

Down conductors and leads

The collector plates can be used to draw current outside the battery. Such collector plates are electrically connected to the collectors and terminals and open beyond the multilayer sheet, which is an external element of the battery.

The material constituting the collector plates is not particularly limited and may be a high conductive material traditionally used for collector plates for lithium-ion batteries. For example, the constituent material for the collector plates is preferably a metal material such as aluminum, copper, titanium, nickel, stainless steel (SUS), or an alloy thereof. The material is more preferably aluminum or copper, taking into account lightness, corrosion resistance and high electrical conductivity. The collector plates of the positive electrode and the collector plates of the negative electrode can be made of the same material or can be made of different materials.

A positive pin terminal and a negative terminal pin are used as needed. The positive terminal and the negative terminal may be conventionally used for lithium-ion batteries. Each part exposed outside the outer battery element 29 is preferably coated with, for example, a heat-shrinkable tube having a heat-resistant insulating property. This reduces the likelihood of negative effects on the surrounding products (for example, components in the vehicle, in particular electronic devices) caused by a short circuit due to contact with peripheral devices or wires.

External battery cell

As an external battery cell 29, a known casing in the form of a metal box can be used. Alternatively, a capsule-shaped casing may be used, allowing coating of the electric power generating element and the use of a multilayer film containing aluminum. The multilayer film may be a film having a three-layer structure in which PP, aluminum and nylon are layered in this order, but not limited to this. A multilayer film is preferred due to its high power and cooling characteristics, as well as its suitability for use in a battery for large devices such as EV and HEV.

The lithium ion secondary battery described above can be manufactured by a conventionally known method.

Appearance configuration of a lithium-ion battery

4 is a perspective view showing an appearance of a flat multilayer lithium ion secondary battery.

As shown in FIG. 4, the multilayer battery 10 has a flat rectangular shape, and the positive electrode collector plate 25 and the negative electrode collector plate 27 for current extraction protrude from both sides of the multilayer battery 10. The power generating element 21 is placed in the outer cell element 29 of the multilayer battery battery 10, and its outer boundary is thermally fused. The electric power generating element 21 is tightly sealed while the positive electrode collector plate 25 and the negative electrode collector plate 27 protrude. The electric power generating element 21 is obtained in such a way that several layers 19 of the unit cells (unit cells) formed from the positive electrode (layer 13 of the active material of the positive electrode), layer 17 of the electrolyte and the negative electrode (layer 15 of the active material of the negative electrode) are stacked on top of each other.

The protrusion state of the collector plate 25 of the positive electrode and the collector plate 27 of the negative electrode from the external battery element 29 shown in FIG. 4 is not particularly limited. The positive electrode collector plate 25 and the negative electrode collector plate 27 may protrude from the identical side. Alternatively, each of the multiple collector plates 25 of the positive electrode and collector plates 27 of the negative electrode may protrude separately from each side. Namely, the protrusion state of the collector plate 25 of the positive electrode and the collector plate 27 of the negative electrode from the external battery element 29 is not limited to the state shown in FIG.

A lithium-ion secondary battery is illustrated as an electrical device in the present embodiment. However, the present embodiment is not limited to this and is applicable to other types of secondary batteries and, in addition, to primary cell batteries. In addition, the present embodiment is applicable not only to batteries, but also to capacitors.

EXAMPLES

Although the present invention is explained in more detail with reference to examples, it is not limited to these examples.

Example 1

An aqueous dispersion of aluminosilicate fine particles as a composition for heat-resistant insulating layers is applied by means of a device with a doctor blade for coating both surfaces of a finely porous film based on polyethylene (PE) as a porous polymer-based substrate. The fine-porous polyethylene film has a film thickness of 18.9 μm and a porosity of 42%. Aluminosilicate fine particles have an average secondary particle diameter of 1 μm and a melting point of 1000 ° C or higher. The aqueous dispersion of aluminosilicate fine particles has a solids concentration of 40% by weight. The aqueous dispersion is then dried by means of warm air, so that heat-resistant insulation layers are formed, thereby preparing a separator having heat-resistant insulation layers. The separator having heat-resistant insulating layers has a width of 200 mm and forms a roll shape.

Although heat-resistant insulation layers are applied to each surface so that they have a thickness of 2.8 μm or more, the actual resulting heat-resistant insulation layer on one side has a greater thickness (3.1 μm) than the actual heat-resistant insulation layer on the other side ( 2.5 μm). The total thickness of the separator having heat-resistant insulation layers is 24.5 μm, and the porosity of the corresponding heat-resistant insulation layers is 47%.

Examples 2-12, comparative examples 1-4

A separator having a porous polymer-based substrate and heat-resistant insulating layers is prepared for the respective examples, as shown in table 1, in a manner analogous to example 1.

However, in each of Examples 2, 3, 6, 11 and Comparative Example 2, a finely porous polypropylene (PP) film (porosity 55%) was used as a polymer-based porous substrate instead of a finely porous polyethylene film.

In each of examples 4, 5, 7, 9, 10 and comparative example 3, a fine-porous film based on polyethylene (PE) (porosity 52%) was used as a porous polymer-based substrate instead of a polyethylene fine-porous film (porosity 42%).

In Example 8, a nonwoven fabric made from polyethylene terephthalate (PET) was used as a polymer-based porous substrate instead of a fine-porous polyethylene film. A nonwoven fabric made from polyethylene terephthalate has a film thickness of 11.1 μm and a porosity of 48%.

In each of comparative examples 1, 4 and 5, a fine-porous film based on polyethylene (PE) (porosity 42%) was used as a porous polymer-based substrate.

In each of examples 2-7, 10, 11, comparative examples 2 and 3, high-purity alumina particles were used as heat-resistant particles instead of the aluminosilicate in example 1. High-purity alumina particles have an average secondary particle diameter of 1.5 nm and a melting point of 1000 ° C or higher.

In Example 8, an ethyl methyl ketone dispersion for colloidal silica particles was used instead of the aluminosilicate aqueous dispersion in Example 1. The colloidal silica particles have an average secondary particle diameter of 0.4 μm and a melting point of 1000 ° C or higher. The dispersion of ethyl methyl ketone has a solids concentration of 30% by weight.

In Example 9, cross-linked polymethyl acrylate particles were used instead of the aluminosilicate aqueous dispersion in Example 1. The cross-linked polymethyl acrylate particles had an average secondary particle diameter of 1 nm and a softening point of about 160 ° C.

In Example 12, a NMP dispersion of an aromatic polyamide (aramid) polymer was used to formulate heat-resistant insulating layers to which ethylene glycol was added so as to obtain porous layers.

Reference Example 5

Operations similar to those of Example 1 are repeated except that a heat-resistant insulating layer is applied to one surface of the porous polymer-based substrate, thereby preparing a separator.

Table 1 summarizes the thicknesses A ′, A ”(μm) of the heat-resistant insulation layers, the total thickness C (μm) and the porosity D (%) of the heat-resistant insulation layers in the separator obtained in each of Examples 1-12 and Comparative Examples 1-5.

Bending height

The bending height of the separator prepared in each of the examples and comparative examples is measured as follows. Firstly, as shown in FIG. 5, a substantially rectangular fragment is cut out of the separator roll and placed on a horizontal surface, and then static electricity is eliminated by cleaning the fragment twice with an antistatic brush. Then, the lift height from the horizontal surface after 60 seconds is measured in each of the eight sections A-H shown in FIG. 5 so as to set the maximum value as the bend height (mm). In the case of rolling, the rolled part opens and stretches upward, and due to this, the height is measured.

Battery rating

Aluminum foil and copper foil are prepared as the collector of the positive electrode and the collector of the negative electrode, respectively. Lithium, cobalt, nickel and manganese oxide (LiNi _0.33 Co _0.33 Mn _0.33 O ₂ ) is used as the active material of the positive electrode in order to prepare a suspension for the active material of the positive electrode. Artificial graphite is used as the active material of the negative electrode in order to prepare a suspension for the active material of the negative electrode. A suspension for the active material of the positive electrode and a suspension for the active material of the negative electrode are applied to the aluminum foil as the collector of the positive electrode and to the copper foil as the collector of the negative electrode, respectively. They are then dried and pressed by rolling in order to prepare a positive electrode and a negative electrode. The separator prepared in each of the examples and comparative examples is placed between the positive electrode and the negative electrode obtained in this way, a non-aqueous electrolyte solution is poured into it, and they are sealed in a multilayer sheet in order to prepare the battery for evaluation. The non-aqueous electrolyte solution used is prepared in such a way that LiPF _{6 is} dissolved, at a concentration of 1.0 ml / l, in a mixed solvent of ethylene carbonate: ethyl methyl carbonate = 1: 2 (volume ratio).

After preparing each battery, the battery undergoes an initial charge and discharge in order to measure the battery capacity. The initial discharge capacity is 20 mA / h. Regarding the battery, the discharge capacity at 4.0 mA and the discharge capacity at 50 mA are measured in order to set the ratio (discharge capacity at 50 mA / discharge capacity at 4.0 mA) as a characteristic of the yield of suitable products (relative yield of suitable products) (%).

Table 1 shows the result of yield characteristics in each of the examples and comparative examples. 6 shows the relationship between parameter X and the height of the bend, and FIG. 7 shows the relationship between parameter Y, the height of the bend and yield characteristics.

Table 1 Polymer-based porous substrate Heat resistant particle A '(μm) A ”(μm) A '+ A ”(μm) A '/ A ” C (μm) D (%) X Y Bending height (mm) Relative yield (%) Example 1 PE Aluminosilicate 3,1 2,5 5,6 1,240 24.5 47 0.15 0.32 4.8 92 Example 2 PP Aluminium oxide 3,5 3.3 6.8 1,061 25.0 42 0.24 0.58 2,3 89 Example 3 PP Aluminium oxide 4.9 3.9 8.8 1,256 29.8 38 0.19 0.49 2,8 93 Example 4 PE Aluminium oxide 5.9 4,5 10,4 1,311 23.5 77 0.26 0.33 3.4 94 Example 5 PE Aluminium oxide 4,5 4.1 8.6 1,098 25.7 53 0.28 0.52 3.0 90 Example 6 PP Aluminium oxide 7.8 6.8 14.6 1,147 29.5 56 0.38 0.67 1,5 87 Example 7 PE Aluminium oxide 3.2 3.0 6.2 1,067 27,2 45 0.20 0.45 3.4 88 Example 8 PET non-woven fabric Silica 1.8 1,6 3.4 1,125 14.5 45 0.19 0.41 2.6 92 Example 9 PE PMMA 2,8 2.7 5.5 1,037 18.1 45 0.28 0.63 2.0 92 Example 10 PE Aluminium oxide 9,4 8.3 17.7 1,133 31.5 51 0.44 0.86 1.3 73 Example 11 PP Aluminium oxide 8.9 7.4 16.3 1,203 33,4 44 0.34 0.77 1.3 79 Example 12 PE Aramid 4.2 3.9 8.1 1,077 22.1 42 0.33 0.79 2.2 78 Comparative Example 1 PE Aluminosilicate 3.2 2,5 5.7 1,280 26,4 67 0.13 0.20 7.9 91 Reference Example 2 PP Aluminium oxide 1.9 1,6 3,5 1,188 30.3 44 0.08 0.19 10.3 90 Reference Example 3 PE Aluminium oxide 2,3 2.1 4.4 1,095 27.8 56 0.13 0.24 6.3 89 Reference Example 4 PE Aluminosilicate 2,8 2.0 4.8 1,400 21,2 45 0.12 0.26 9.5 93 Reference Example 5 PE Aluminosilicate 5.8 - 5.8 - 21,2 45 - - 26 91

The parameter X of each of the separators prepared in examples 1-12 is greater than or equal to 0.15. The bend height of each of examples 1-12 is less than or equal to 5 mm. Thus, problems with the separator do not arise even when laying by using a continuous flat lay machine. When using a machine for continuous flat layering, the process, which includes the steps of cutting with a heated knife, transferring with a porous suction cup and laying with a four-point lock, is repeated several tens of times. As a result, the bend is not detected in the edge portions during installation. It should be noted that the process, which includes the steps of cutting with a heated knife, transferring with a porous suction cup and laying with a four-point lock, takes about three seconds.

Some parts of the separators prepared in comparative examples 1-4 are bent during transfer to the electrodes by using a continuous flat lay machine. As a result, each separator is layered in a multilayer object with a pressed bent part, and therefore the separator is not applicable. In particular, in comparative example 5, in which only one side of the separator is machined, the separator bends immediately after cutting. As a result, the transfer itself is impossible.

Regarding the yield characteristics, the separators prepared in examples 1-9 demonstrate a parameter Y in the range of 0.3-0.7 and provide sufficient power characteristics in excess of 85%. In each of examples 10-12, in which the parameter Y exceeds 0.7, the yield characteristic is below 85%, and the characteristics are slightly insufficient for the product.

These results reveal that bending can be prevented by adjusting the thicknesses of the heat-resistant insulation layers relative to the total thickness of the separator and by controlling the balance between the thicknesses of the heat-resistant insulation layers on both sides of the separator.

In addition to the conditions described above, it has been found that a battery having high power characteristics can be obtained by adjusting the thickness and porosity of the respective heat-resistant insulating layers.

Although the present invention has been described above with reference to examples, the present invention is not limited to their description, and it will be apparent to those skilled in the art that various modifications and improvements can be made.

INDUSTRIAL APPLICABILITY

In a separator having heat-resistant insulation layers according to the present invention, the stress balance of compressing heat-resistant insulation layers on both sides of the separator is improved by controlling the thickness of the respective heat-resistant insulation layers on both sides and the total thickness of the separator. In addition, the balance between the internal mechanical stress of the porous polymer-based substrate and the mechanical stress during compression of the heat-resistant insulating layers is improved. Accordingly, the bend does not form unhindered during layering, so that an electrical device having high reliability can be stably manufactured.

LIST OF REFERENCE POSITIONS

1 - a separator having heat-resistant insulating layers (separator)

2 - a porous polymer-based substrate

3 - heat-resistant insulating layer

4 - positive electrode

5 - negative electrode

10 - multilayer battery (lithium-ion battery)

11 - current collector of the positive electrode

12 - negative electrode current collector

13 - layer of active material of the positive electrode

15 - layer of the active material of the negative electrode

17 - electrolyte layer

19 - a layer of single galvanic cells

21 - electric power generating element

25 - current collector plate of the positive electrode

27 - current collector plate of the negative electrode

29 - external battery element (multilayer film).

Claims (8)

1. A separator having heat-resistant insulating layers for an electrical device, the separator comprising:
a porous polymer based substrate and
heat-resistant insulating layers formed on both surfaces of a porous polymer-based substrate and containing heat-resistant particles having a melting point or thermal softening point of 150 ° C or higher,
the parameter X represented by the following mathematical formula 1 is greater than or equal to 0.15:

where A ′ and A ″ are the thicknesses (μm) of the respective heat-resistant insulating layers formed on both surfaces of the porous polymer-based substrate when the condition A ′> A ″ is satisfied, and C is the total thickness (μm) of the separator having heat-resistant insulation layers ;
moreover, the thickness of the porous polymer-based substrate is in the range from 1 to 200 μm, and the total thickness of the heat-resistant insulating layers is in the range from 5 to 200 μm;
the parameter Y, represented by the following mathematical formula 2, is in the range of 0.3-0.7:

where D represents the porosity (%) of the corresponding heat-resistant insulating layers. 2. The separator according to claim 1, in which the parameter X is greater than or equal to 0.20. 3. The separator according to claim 1, in which the heat-resistant particles are particles of an inorganic oxide. 4. The separator according to claim 1, in which the heat-resistant particles are particles of an organic polymer. 5. The separator according to claim 1, in which the porosity of the corresponding heat-resistant insulating layers is in the range of 40-70%. 6. The separator according to claim 1, in which the ratio of the thicknesses (A ′ / A ″) of the heat-resistant insulating layers is in the range of 1.037-1.2. 7. An electrolyte layer for an electrical device, comprising:
a separator having heat-resistant insulating layers according to claim 1; and an electrolyte contained in a porous polymer-based substrate and in heat-resistant insulating layers of a separator having heat-resistant insulating layers. 8. An electrical device containing a separator having heat-resistant insulating layers, according to claim 1.

Images